The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form switching power supply controllers, such as pulse width modulated (PWM) power supply controllers, that were used to regulate the value of a voltage supplied by a power supply system. In some cases, the switching power supply controllers were capable of operating in a fixed frequency mode during normal operation. When the current required by the load that was receiving power from the power supply system decreased, some of the prior switching power supply controllers operated in a light load mode that skipped some of the PWM cycles. In most cases, the cycle skipping operation was inefficient and also could produce undesirable electromagnetic interference. Additionally, the skip-cycle mode often resulted in high ripple in the output voltage. Some other PWM controllers operated in a hysteretic mode. The hysteretic operation was asynchronous and was difficult to use in multi-channel PWM controllers. Some other controllers operated in a constant on-time mode. These controllers were also asynchronous which could result in frequency beating problems between channels of a multi-channel system.
Accordingly, it is desirable to have a power supply controller that operates under light load conditions with improved efficiency and reduces the amount of electromagnetic inference.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.